1. Field of the Invention
The present invention generally relates to semiconductor devices, and more particularly to a semiconductor device including a heat dissipation member that dissipates heat generated in a semiconductor element.
2. Description of the Related Art
In recent years, semiconductor elements provided inside semiconductor devices have become higher in density and speed. As a result, the amount of heat generated during operation has been on the increase. On the other hand, there is a demand for smaller semiconductor devices.
Accordingly, there is a demand for a semiconductor device that can dissipate heat generated in a semiconductor element with efficiency while being reduced in size.
For instance, International Publication No. WO98/49726 (Patent-Related Document 1) and Japanese Laid-Open Patent Applications No. 2000-216284 (Patent-Related Document 2), No. 2001-168244 (Patent-Related Document 3) and No. 2003-204015 (Patent-Related Document 4) disclose conventional semiconductor devices including a heat dissipation member. According to the semiconductor device disclosed in Patent-Related Document 1, interconnection lines are formed on an insulating substrate so that one end of each interconnection line is connected to a semiconductor element by a wire and an external electrode is provided to the other end of each interconnection line. The semiconductor element is thermally coupled to a metal plate (a heat dissipation plate) provided to the insulating substrate. However, according to the semiconductor device of Patent-Related Document 1, a circuit board formed of the interconnection lines and the insulating substrate is pressed. Accordingly, there is a problem in that the circuit board is restricted in material selection. Further, since pressing is employed, there is a problem in that it is difficult to obtain dimensional accuracy that enables narrow pitch.
The semiconductor device disclosed in Patent-Related Document 2 is of a BGA (Ball Grid Array) type. Press punching is performed on the first and second heat sinks and the circuit board of the semiconductor device in order to form a recess in its semiconductor element part. Accordingly, there is also a problem in that the circuit board and the heat sinks are restricted in material selection in the semiconductor device of Patent-Related Document 2.
Further, the semiconductor element and the electric circuit board are connected by wire bonding, and the electrode surface of the semiconductor element and a surface on which solder balls (external connection terminals) are provided are in the same plane. Accordingly, there is a problem in that the solder balls are restricted in size and wire bonding is restricted in loop shape in order to prevent mutual interference.
The semiconductor device disclosed in Patent-Related Document 3 is also of a BGA type, and requires press working in order to form a recess for containing a semiconductor element part in a heat spreader. Accordingly, in Patent-Related Document 3, there is also a problem in that the semiconductor device is increased in size. Further, a semiconductor element and an electric circuit board are connected by wire bonding, and a surface on which solder balls are provided and a surface on which wires are provided are in the same plane. Accordingly, there is a problem in that the size of the solder balls and the loop shape of wire bonding are subject to restrictions in sealing the semiconductor element with resin.
Meanwhile, no press working is performed on the semiconductor device disclosed in Patent-Related Document 4, in which a metal base serving as a heat dissipation plate is like a flat plate. Further, a semiconductor element and interconnection lines formed on an insulating layer are connected with wires, and an interposer substrate is provided on the insulating layer on which the interconnection lines are formed. Since solder balls are formed on the interposer substrate, the loop height of wire bonding is offset by the thickness of the interposer substrate. Accordingly, the loop height of wire bonding and the ball size of the solder balls can be set as desired without mutual interference. Thus, the semiconductor device disclosed in Patent-Related Document 4 can eliminate the disadvantages of the above-described semiconductor devices of Patent-Related Documents 1 through 3, and can be reduced in cost, higher in reliability, narrower in pitch, and reduced in size.
However, according to the semiconductor device of Patent-Related Document 4, a resin substrate is provided between the semiconductor element and the metal base serving as a heat dissipation plate. This prevents efficient transfer of heat generated in the semiconductor element to the metal base, thus resulting in the problem of poor heat dissipation characteristics.